Method for mixing pressure gases particularly for respirators and medical devices

ABSTRACT

In a method for mixing two gases in a predetermined ratio, the two gases are supplied to respective chambers, having fixed or adjustable preselected volumes, through respective first pressure regulators while maintaining the discharge pressures of the two first pressure regulators in such predetermined ratio. The flow of the two gases to the chambers is then interrupted, and the two gases are thereafter discharged from the respective chambers to a common discharge line through respective second pressure regulators while maintaining the discharge pressures of the two second pressure regulators in such predetermined ratio. The apparatus includes adjustable means for conjointly adjusting both the first and second pressure regulators so that the discharge ratios thereof are equal and equal to the predetermined ratio. A reversing shut-off valve may be used to connect the chambers to the first pressure regulators or to discharge the chambers through the second pressure regulators. A magnetically biased torsion resistant lever may be used to commonly bias the pressures of the first and second pressure regulators and also to adjust the respective pressure ratios. The respective first and second pressure regulators for each gas may be combined into a single unit.

United States Patent Dobritz [54] METHOD FOR MIXING PRESSURE GASESPARTICULARLY FOR RESPIRATORS AND MEDICAL DEVICES Gunter Dobritz, Lubeck,Germany Dragerwerk Aktiengesellschaft, Lubeck, Germany [22] Filed: June11, 1970 [21] Appl.No.: 45,372

[72] Inventor:

[73] Assignee:

[30] Foreign Application Priority Data June 20, 1969 Germany ..P 19 31354.3

1151 3,669,134 1 June 13, 1972 3,515,155 6/1970 Hafi'ner et a1 ..137/73,524,444 8/1970 Ellard et al.... ....l37/ll1 X 3,530,873 9/1970 Arp eta1 ..137/99 Primary Examiner-$amuel B. Rothberg Assistant Examinen-DavidJ. Zobkiw Auorney-McGlew and Toren [57] ABSTRACT second pressureregulators while maintaining the discharge pressures of the two secondpressure regulators in such predetermined ratio. The apparatus includesadjustable means for conjointly adjusting both the first and secondpressure regulators so that the discharge ratios thereof are equal andequal to the predetermined ratio. A reversing shut-off valve may be usedto connect the chambers to the first pressure [56] References Citedregulators or to discharge the chambers through the second UNITED STATESPATENTS pressure regulators. A magnetically biased torsion resistantlever may be used to commonly bias the pressures of the first 2,527,13610/1950 Kag1e ta1 ..222/57 X and second pressure regulators and also [0adjust the respec 2,733,953 4/1957 Schneider-H "137/1 11 X tive pressureratios. The respective first and second pressure 3,032,053 5/ l 962 Rosset l l l regulators for each gas may be combined into a single unit.3,068,864 12/1962 Tietze 128/147 3,298,383 l/1967 Cooper ..137/7 X 2Claims, 4 Drawing Figures A P B 5 e 3 G s A-- 1 1- -----1 21- L- l0 P 47 a P Gas B B A B Gosh- METHOD FOR MIXING PRESSURE GASES PARTICULARLYFOR RESPIRATORS AND NIEDICAL DEVICES BACKGROUND OF THE INVENTION Thereare known methods and known apparatus for mixing gas currents. In onemethod, two pressure gases are expanded, each through a respectivethrottle valve and a respective flowmeter, into a common exhaust pipe,with the mixing ratio of the gases being adjusted in the flowmeters.This method has the disadvantage that the flowmeters and the throttlevalves must be constantly monitored. Additionally, it must be assuredthat a certain pressure is always maintained in the flowmeters, asotherwise the readings of the flowmeters will not be correct. Thus, itis also necessary to maintain exactly a certain discharge gas pressure.In practice, this method can work satisfactorily only at flow velocitiesabove a certain value, namely, in the so-called supercritical range.This is a disadvantage, since this range cannot be maintained safelyusing simple means.

In another known method, two pressure gases are expanded to atmosphericpressure, drawn in by means of piston pumps having a variable strokevolume, and forced into the common discharge pipe. This method has thedisadvantage that it requires a large amount of equipment, like pistonpumps, drives therefor, and control devices.

SUMMARY OF THE INVENTION This invention relates to the mixing of twogases in a predetermined ratio and, more particularly, to a novel methodof and apparatus for performing such mixing and which permits theproduction of a mixture of two pressure gases, properly set to a certainratio, utilizing simple means and avoiding the above-mentioneddisadvantages.

In the method of the invention, each of the two gases to be mixed issupplied to a respective chamber having a predetermined or adjustablevolume, through a separate pressure regulator. The pressure regulatorsare interconnected with each other in such a way that the discharge gaspressures thereof are in an adjustable predetermined ratio to eachother, the two pressure regulators constituting what will be termedhereinafter a first pressure ratio regulator". After such supplying ofthe two chambers, the gas flow is interrupted and the gases aredischarged from the respective chambers through a second pressure ratioregulator which is set to the same pres sure ratio as the first pressureratio regulator, the second pressure ratio regulator discharging intothe common discharge pipe for the gas mixture. With the inventionmethod, it is possible to produce, with simple means, a gas mixture of adesired concentration ratio since a certain quantity or amount of eachgas to be mixed is measured, after which the measured quantities aredrawn off and mixed exactly according to the measured quantitativeratio.

In a simple form of the method, the two chambers have the same volume,and the ratio of the filling pressures of the gases to be mixed is setin accordance with the desired mixing ratio. With this arrangement, itis possible, with simple means, to set the mixing ratio to therespective required value.

In the invention apparatus, each chamber, having a preselected oradjustable volume, is connected, through a first pressure regulator anda first shut-off valve, to a feed or supply pipe, and is connected,through a second shut-01f valve and an additional or second pressureratio regulator to a common gas discharge pipe for the gas mixture. Inusing the apparatus of the invention, during the filling process, thechambers are filled with the gases to be mixed later in correspondencewith the adjustable pressure ratio of the pressure ratio regulator. Whenthe chambers are discharged, the gases expand through the shut-ofi'valves and the second pressure ratio regulator into the mixturedischarge pipe.

The pressure ratios of both pressure ratio regulators are adjustable,but the pressure ratios of both pressure ratio regulators are the samefor a certain gas mixing ratio. The pressure ratio regulators can bearranged either upstream or downstream of the associated shut-offvalves.

An object of the invention is to provide a simple and improved methodfor mixing two gases in a predetermined ratio.

Another object of the invention is to provide a simple and improvedapparatus for mixing two gases in a predetermined ratio.

A further object of the invention is to provide such a method andapparatus in which the two gases are supplied to respective chambersthrough a first pressure ratio regulator, the flow of the two gases isinterrupted, and the two gases are discharged through a second pressureratio regulator.

Another object of the invention is to provide such a method andapparatus in which the ratios of the two pressure regulators aremaintained equal to each other and equal to the desired predeterminedratio of the gas mixture.

For an understanding of the principles of the invention, reference ismade to the following description of typical embodiments thereof asillustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic flow diagram illustrating the apparatus of theinvention;

FIGS. 2 and 3 are part schematic, part sectional and part perspectiveviews illustrating alternative embodiments of the apparatus of theinvention; and

FIG. 4 is a view similar to FIGS. 2 and 3 illustrating a simplified formof the apparatus shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1,chambers l and 2 are filled periodically with a preselected oradjustable volume of the pressure gases A and B, and are subsequentlydischarged into storage tank 3 and thence into gas mixture mixturedischarge pipe 10. During filling of chambers l and 2, the two shutoffvalves 6 and 7 are closed and the two shut-off valves 4 and 5 are open,so that pressure gases A and B can flow into respective chambers l and 2through pressure ratio regulator 8. The ratio of the pressures inchambers l and 2 depends on the setting of pressure ratio regulator 8.After closing shut-off valves 4 and 5 and opening shut-off valves 6 and7, discharge of the chambers is effected through pressure ratioregulator 9, which must be set to the same pressure ratio as that towhich pressure ratio regulator 8 is set. Discharge is efi'ected intostorage tank 3 and from there into mixture discharge pipe 10. As a rule,only one chamber is expanded to the pressure in the discharge pipe,while the other maintains a residual pressure corresponding to the setpressure ratio.

In the embodiment of the invention shown in FIG. 2, the two pressure gaspipes 11a and 1 lb, through which the gases A and B are supplied, leadto pressure ratio regulator 12. The latter comprises two housings 13aand 13b having inlet ports 14a and 14b which form valve seats for therespective moving valve bodies 15:: and 15b. The valve bodies areconnected with the respective control diaphragms 16a and 16b which closethe pressure chambers 17a and 17b. Pipes or conduits 18a and 18b leadfrom pressure chambers 17a and 17b, respectively, to the gas distributorwhich contains the shut-off valves, and which are represented, in FIG.2, as a reversing valve 19.

Reversing valve 19 can be designed in various ways, and its function isto connect lines 18a and 18b simultaneously either with the respectivelines 20a and 20b, leading to chambers 21a and 21b having either thesame or different volumes, or to interrupt this connection andsimultaneously to connect pipes or lines 20a or 20b to pipes or lines22a and 22b which lead, through an additional pressure ratio regulator23, to storage tank 24.

In the illustrated embodiment, reversing valve 19 is designed as a slidevalve where the port communicating with line a is arranged between theports communicating with lines 18a and 22a and the port leading to line20b is arranged between the ports communicating with lines 18b and 22b.Reversing valve 19 is controlled by control rod 25 on which there aresecured the shut-ofi discs 26, 27, 28 and 29. In the representedposition, lines 18a and 18b are connected to respective lines 20a and20b. When control rod 25 is moved into its other position, lines 20a and20b are connected with the respective lines 22a and 22b.

Diaphragms 16a and 16b of pressure ratio regulator 12 are connected witheach other through a rocker arm 30 whose bearing 31 can be displaced inthe direction of the double arrow 32. By such displacement, the ratio ofthe lever arms 1 and I can be adjusted, and the pressure ratio inpressure chambers 17a and 17b thus can be set. Diaphragms 16a and 16bwhich are subjected, on one side, to the gas pressure in chambers 17aand 17b, respectively, and are subjected on the opposite side with anydesired but constant pressure, for example, atmospheric pressure. Thepressure ratio in chambers 17a and 17b is established in accordance withthe following equation:

Equation 1 oona!) 2 (PB mnst) Since bearing 31 is connected by a member33 with bearing 34, the same pressure ratio is set in both pressureratio regulators 12 and 23. The adjusted position of connecting member33 is indicated by a pointer 35 on a scale 36, and shows the setting ofthe pressure ratio of both pressure ratio regulators 12 and 23.

A rocker 37, having the bearing 34, connects control diaphragms 38a and38b of pressure ratio regulator 23, on which are secured the respectivemoving valve bodies 39a and 39b. These valve bodies cooperate with thevalve seats formed by the outlet ports 40a and 40b of the respectivehousings 41a and 41b. The pressure chambers of housings 41a and 41b areconnected with storage tank 24 by respective discharge lines 420 and42b.

The method of operation of this embodiment of the apparatus will now bedescribed. In the represented position of reversing valve 19, pressuregases A and B flow through lines 11a and 11b, respectively, throughrespective inlet ports 14a and 14b and into the respective pressurechambers of housings 17a and 17b. From there the gases flow through therespective lines 18a and 18b, through reversing valve 19, and throughrespective lines 20a and 20b into respective chambers 21a and 21b. Thefinal pressure in chambers 21a and 21b is formed in accordance withequation 1. After chambers 21a and 21b have been filled, they can bedischarged into storage tank 24 by switching reversing valve 19.Discharge is effected through respective pipe lines 20a and 21b,reversing valve 19, respective lines 22a and 22b, the pressure chambersof respective housings 41a and 41b, respective outlet ports 40a and 40b,and respective pipes or lines 42a and 42b. During the discharge of thechambers, the pressure ratio regulator 23 also satisfies equation 1 forthe chambers 21a and 21b.

Switching of reversing valve 19 can be effected in dependence on time,and can be controlled, for example, in dependence on a time signaltransmitter. However, reversing valve 19 also can be controlled independence on the pressure in chambers 21a and 21b, or in dependence onthe pressure in storage tank 24, or in response to other controlquantities.

The embodiment of the invention illustrated in FIG. 3 differs from thatillustrated in FIG. 2 in that the two pressure ratio regulators l2 and23, as well as the reversing valve 19, are combined to form a unit.Referring to FIG. 3, pressure gas pipes 43a and 43b, through which therespective gases A and B are supplied, carry the respective inlet ports44a and 44b of respective housings 45a and 45b, and which inlet portsform the valve seats for the respective valve bodies 46a and 46b loadedby respective springs 63a and 63b. The outlet ports 47a and 47b in therespective diaphragms 48a and 48b, forming the valve seats of therespective additional valve bodies 46c and 46d connected fixedly withrespective valve bodies 46a and 46b, are connected with storage tank 50.The pressure chambers 51a and 5 lb of the respective housings 45a and45b are connected through respective lines 52a and 52b with respectivechambers 53a and 53b of a preselected or adjustable volume. The twodouble diaphragms, one comprising diaphragms 48a and 54a interconnectedby bridge 55a, and the other comprising diaphragms 48b and 54b,interconnected by bridge 55b, are connected with each other through arocker 56. Rocker 56 has a bearing point 58 which can be displaced inthe direction of the arrow 57, and which can assume two end positions,fixed in the directions of the arrow 59in dependence on the force actingon this bearing, and which force is produced by the difierentialpressures on the double diaphragms 48a, 54a, and 48b, 54b. In theembodiment of FIG. 3, this force is provided by the bearing point 58bearing against a torsion-resistant lever 60 connected with an ironbridge 61 which is under the influence of a magnet 62 which tends topull bridge 61 downwardly. The upper limit of move ment is provided by astop 64.

The embodiment of the invention shown in FIG. 3 operates in a mannerwhich will now be described. With lever 60 in the represented position,pressure gases A and B flow through respective pipes 43a and 43b throughrespective inlet ports 44a and 44b into the respective pressure chambers51a and 5 lb, and then through respective lines 52a and 52b into therespective chambers 53a and 53b. During the filling, the pressure ratioin chambers 53a and 53b is established, at any time, according toequation 1. If the sum of the forces produced by the differentialpressures on double diaphragms 48a, 54a and 48b, 54b exceeds the holdingforce exerted by magnets 62, lever 60 is biased into the upper endposition in the direction of the arrow 59. In this position, inlet ports44a and 44b are closed by the respective valve bodies 46a and 46b biasedby respective springs 63a and 63b. The pressure gases can expand throughthe simultaneously opened outlet ports 47a and 47b from chambers 53a and53b, respectively, through lines 52a and 52b, respectively, therespective pressure chambers 51a and 51b, the respective outlet ports47a and 47b, and the respective lines 49a and 49b into the storage tank50. During such discharge of the gases, the pressure ratio in chambers53a and 53b is satisfied, at any time, by equation 1. If the sum of theforces produced by the differential pressures on the double diaphragms48a, 54a and 48b, 54b are less than the holding force exerted by magnets62, lever 60 is biased into he downward end position in the direction ofarrow 59, and a new filling operation is initiated.

FIG. 4 illustrates a simplification of the embodiment illustrated inFIG. 3. Double diaphragms 48a, 54a and 48b, 54b are now formed as singlediaphragms 65a and 65b, respectively, having respect outlet ports 66aand 66b which permit the passage of gases, during discharge fromrespective chambers 67a and 67b to flow through container or enclosure68 and discharge pipe 69 into storage tank 70. The exact pressure ratioaccording to equation 1 is met, however, only if the back pressure ondiaphragms 65a and 65b is constant. Care therefore must be taken sothat, by proper dimensioning of the apparatus, the back pressure ondiaphragms 65a and 65b remains practically constant during the fillingand during the discharge.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it should be understood that the invention may beembodied otherwise without departing from such principles.

What is claimed is:

l. A method for mixing two gases in a predetermined ratio, comprisingthe steps of supplying the two gases to respective chambers, havingrespective preselected volumes, through respective first pressureregulators while maintaining the discharge pressures of the two firstpressure regulators in such predetermined ratio; simultaneouslyinterrupting the flow of both gases into the respective chambers; andthereafter discharging the two gases from the respective chambers to acommon discharge line through respective second pressure regulatorswhile maintaining the discharge pressures of the two second pressureregulators in such predetermined ratio.

2. A method as claimed in claim 1, in which the chambers have the samepreselected volume and are filled to respective pressures having suchpredetermined ratio. 5

1. A method for mixing two gases in a predetermined ratio, comprisingthe steps of supplying the two gases to respective chambers, havingrespective preselected volumes, through respective first pressureregulators while maintaining the discharge pressures of the two firstpressure regulators in such predetermined ratio; simultaneouslyinterrupting the flow of both gases into the respective chambers; andthereafter discharging the two gases from the respective chambers to acommon discharge line through respective second pressure regulatorswhile maintaining the discharge pressures of the two second pressureregulators in such predetermined ratio.
 2. A method as claimed in claim1, in which the chambers have the same preselected volume and are filledto respective pressures having such predetermined ratio.